fixes extension letter-case errors

[serdnab]

Hi Nicolas, I'm Andrés and this is my first pull request. This fixes #143, #140 and other extensions letter-case related errors. Regards.

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[serdnab]

I signed the CLA as requested.

[googlebot]

CLAs look good, thanks!

[nicolasgarnier]

Looks good thanks @serdnab !

[nicolasgarnier]

Pushed!